FRIENDS AND FISH

The word chum poses quite an etymological enigma. The definition meaning "friend" emerged in the late seventeenth century among Oxford University students as an affectionate slang term for "roommate" (similarly, chummery was the the name for a shared living space and chummage was the process of splitting up a living space). There's some speculation that this comes from an abbreviation of chamber-fellow or chamber-mate because some early attestations define the word that way and at the time there was a popular fad that involved shortening words. However, this is uncertain and it could just as easily come from a word like comrade. The other definition of chum, "chopped fish", emerged among New England sailors in the mid-nineteenth century and also has an obscure etymology but is not related.